1. Field of the Invention
The present invention relates to a method and an apparatus for inserting additional data, and more particularly, to a method and an apparatus for inserting additional data, such as a watermark, into a Moving Picture Expert Group (MPEG) bitstream without causing excessive coding and degradation of picture quality
2. Description of the Related Art
As the digital technology is advanced, a lot of digital multimedia data has become easily available. Unlike analog information, digital information can be mass-produced at low cost without degrading data quality. Such a characteristic of digital information may become problematic from the point of view of copyright protection. One of technologies for solving the copyright problem of such digital contents employs an insertion of additional data, such as a watermark, into a coded video stream.
Such an additional data insertion scheme is a technology for preventing illegal copy and protecting the copyright of the digital contents by inserting data, such as a user identification (ID) or user information, into the digital contents.
If such additional data is inserted into video data, however, the following problem may occur. In a moving image codec technology, such as High Efficiency Video Coding (HEVC), when coding is performed, coding efficiency is improved using inter-prediction in which reference is made to a previously coded picture or slice. In this case, there is a burden of coding pictures, which refer a picture or slice into which additional data has been inserted, again in series. In particular, such a problem may cause a bigger problem when additional data is inserted after coding is already completed.
FIG. 1 is a schematic diagram for illustrating a method of processing a bitstream with an insertion of additional data when coding a video.
In the example shown in FIG. 1, a bitstream 100 includes an Intra-coded (I) frame, a Predictive-coded (P) picture on which uni-directional inter-prediction is performed, and a Bidirectional-coded (B) picture on which bidirectional inter-prediction is performed.
The bitstream 100 includes a picture A (PA) 110 that is a target into which additional data is to be inserted, a picture B (PB) 120 that refers to the PA 110, and a picture C (PC) 130 other than the PA 110 and the PB 120. In this case, if the additional data is inserted into the PA 110, a decoder that receives the PA 110 is unable to clearly decode the PA 110 with a common decoding. That is, when decoding is performed with the common decoding, picture quality is degraded. Furthermore, the picture qualities of the PB 120 and the PC 130 that refer to the PA 110 directly or indirectly are also degraded. In other words, the PB 120 referring to the PA 110 needs to refer to a picture A′ (PA′) into which additional data has been inserted and needs to be coded again. Whole or a part of the PC 130 that refers to a newly coded PB also needs to be coded again. Accordingly, there are problems in that the coding efficiency is degraded due to repeated codings and there is a big burden in executing the video coding operation due to the insertion of additional data.